A number of different printing methods are used in printing presses. Non-impact printing (NIP) methods are understood as printing methods that do not require a fixed, that is to say, a physically unalterable printing forme. Printing methods of this type are able to produce different printed images in each printing operation. Examples of non-impact printing methods include ionographic methods, magnetographic methods, thermographic methods, electrophotography, laser printing, and in particular inkjet printing methods. Such printing methods typically involve at least at least one image producing device, for example at least one print head. In the inkjet printing method, such a print head is configured, for example, as an inkjet print head and has at least one and preferably a plurality of nozzles, by means of which at least one printing fluid, for example in the form of ink droplets, can be transferred selectively onto a printing substrate. Alternative printing methods, such as intaglio printing, planographic printing, offset printing and letterpress printing methods, in particular flexographic printing, use fixed printing formes. Depending upon the size of the print run and/or other requirements such as print quality, a non-impact printing method or a printing method that uses a fixed printing forme may be preferable.
The precise matching of a printed image on the front and back sides of a printing substrate that is printed on both sides is referred to as register (DIN 16500-2). In multicolor printing, the merging of individual printed images of different colors in precise alignment to form a single image is referred to as color registration (DIN 16500-2). In inkjet printing, as with other processes, appropriate measures must be implemented to maintain color registration and/or register. In particular, it is important for the relative position between print head and printing substrate to be known and/or kept constant. Color registration is also referred to as color register. In the following, the term register mark will therefore also be understood as referring to a registration mark, i.e. a mark for checking color registration or color register.
Sheet-fed printing presses are known. However, conventional transport systems cannot always be used with particularly thick sheets.
From DE 10 2015 111 525 A1, a sheet-fed printing press is known, which operates based upon the principle of offset printing and which is equipped with additional inkjet printing elements that have print heads and dryers, which are optionally movably disposed. Drives for transporting sheets are not described.
From DE 102 27 241 A1, a drive system of a sheet-fed printing press is known, in which drive control units act as module control units.
From DE 10 2011 088 776 B3, a printing press which has inkjet print heads and dryers is known. The transport of printing substrate and drives provided for said transport are described only in connection with a web-fed printing press.
EP 0 669 208 A1 discloses a sheet-fed printing press having drive motors for cylinders and the possibility of positioning said drives axially.
EP 0 615 941 A1 discloses a sheet-fed printing press having individually driven acceleration means.
From WO 2013/163748 A1, a sheet-fed printing press is known, which has a plurality of drives for respective flat belts within a unit, and which operates according to a non-impact printing method.
From WO 2011/064075 A2, a sheet-fed printing press having a flat transport path is known, which has a conveyor belt and a priming system and a finish coating system.
From EP 2 623 330 A, a sheet-fed printing press having a flat transport path is known, which has a conveyor belt. Motors are disclosed only in connection with driven finish coating rollers or a scanning print head movement. Systems for applying primer and/or for applying a finish coating are mentioned.
From DE 101 52 464 A1, a sheet-fed printing press of modular construction having non-impact coating heads is known, which has a separate, dedicated module with a flat transport path for each of a plurality of colors, each such module having its own dedicated drive, or every two such modules having one drive.
From U.S. Pat. No. 8,366,105 B1, a sheet-fed printing press having a flat transport path is known, which has a conveyor belt and a plurality of non-impact print positions, and which, in addition to a feeder module, has a further processing module and a printing module which has a drying system, a plurality of conveyor belts, and respective drive motors.
From US 2006/023023 A1, a sheet-fed printing press is known, in which print heads are movable parallel to a moved printing substrate in order to increase the resolution of the printed image. The print heads are moved by means or a servo motor.
EP 2 712 737 A describes a sheet-fed printing press that has two nozzle modules and a plurality of flat conveyor belts, each having its own separate drive, as the prior art.
From EP1 867 489 A1, a sheet-fed printing device having a printing system and a finish coating system is known. In one alternative, the printing system and the finish coating system each have their own dedicated drive system.
From EP 2 371 561 A2, a sheet-fed printing device in the form of an office printer having two print positions is known, wherein at each of the two print positions print heads are arranged opposite a respective conveyor belt, and wherein each conveyor belt is assigned a respective motor. The first print position can be used for primer application. The motors are controlled to a certain speed. The position of the printing substrate is determined based upon this speed and corresponding time intervals.